Whistling sound from cold air intake

[Grover]

One of the few "teething" issues I've not been able to fix since the install of my stroker EFI motor is a whistling sound that comes under acceleration. Depending on the speed I'm traveling, it takes varying amounts of throttle which leads me to believe it's due to "total" air speed traveling into the manifold. While stationary I've removed various bits of the intake system all the way up to removing the TB boot, but still if I blip the throttle I'm hearing a whistle as air is sucked in. I've not heard of this same issue from others who have done similar conversions. I'm using the 318 intake manifold, 325i TB with the adapter plate from 02Again. For a split second it can sound cool (almost like a turbo whine) but the novelty wears off VERY quickly. Any ideas on what could be causing this and what one can do to reduce or eliminate the noise? Thanks folks.

[KFunk]

Sounds to me like a simple vacuum leak somewhere in the intake path, maybe one of the TB gaskets? I'm not sure how those are set-up.

Did you try spraying some carb cleaner around everywhere while the engine is idling? It should affect the idle speed whenever you hit the leaky spot.

[Grover]

No, I don't think it's from the filter, it's somewhere further upstream so to speak. Even once I pulled the TB boot off I still heard it. I've not tried spraying carb cleaner around there, sounds like that may be worthwhile. Thanks for the idea.

[eastsidebimmer]

Sounds to me like a simple vacuum leak somewhere in the intake path, maybe one of the TB gaskets? I'm not sure how those are set-up.

Did you try spraying some carb cleaner around everywhere while the engine is idling? It should affect the idle speed whenever you hit the leaky spot.

Try spraying something besides carb cleaner to check for vacuum leaks--that crap will remove the finish from your painted surfaces in a hurry.

[Turb02]

I think its just because if the amount of air that is being sucked into the engine. Its kinda hard to explain but there is less restriction on the intake side so you will hear the air flowing thru the cold air intake. It will sound similar with no intake piping and just the throttle body too. Its normal. My 95 M3 has a CAI and it almost overpowers the sound of the custom exhaust I have.

[jgerry2002]

I wonder if you could try swapping in an airbox from another BMW... Like an E36. They are all baffled to reduce noise. Looks like you'd have the room too.

[Turb02]

I wonder if you could try swapping in an airbox from another BMW... Like an E36. They are all baffled to reduce noise. Looks like you'd have the room too.

Kinda defeats the purpose of a cold air intake though, dont you think?

[slash02]

One of the few "teething" issues I've not been able to fix since the install of my stroker EFI motor is a whistling sound that comes under acceleration. Depending on the speed I'm traveling, it takes varying amounts of throttle which leads me to believe it's due to "total" air speed traveling into the manifold. While stationary I've removed various bits of the intake system all the way up to removing the TB boot, but still if I blip the throttle I'm hearing a whistle as air is sucked in. I've not heard of this same issue from others who have done similar conversions. I'm using the 318 intake manifold, 325i TB with the adapter plate from 02Again. For a split second it can sound cool (almost like a turbo whine) but the novelty wears off VERY quickly. Any ideas on what could be causing this and what one can do to reduce or eliminate the noise? Thanks folks.

That cone filter might be it. Mine Whistles too... if you have the E30 filter box thing, try it.. .they are an "intake muffler"

*edit* I just read you don't think it's from the intake side... I'd check intake gaskets and such as well. did you use OEM gaskets on the TB or just some gasket maker goo like me? There's also holes to plug up on the M20 throttle body isnt there? (I cannot remember offhand)

[robspeed]

I wonder if you could try swapping in an airbox from another BMW... Like an E36. They are all baffled to reduce noise. Looks like you'd have the room too.

Kinda defeats the purpose of a cold air intake though, dont you think?

no, because the stock airbox *IS* a cold-air intake! every stock new BMW has a CAI, even my 02 had one...

[Grover]

Thanks guys. As relucatant as I am to put in one of the E30 airboxes (simply because they are so UGLY) I'll give it a try to see if it helps. The shape of the filter I'm using seems to be irrelevant as the noise is happening either with or without it in place. I report back on my findings. Thanks guys.

[slash02]

I wonder if you could try swapping in an airbox from another BMW... Like an E36. They are all baffled to reduce noise. Looks like you'd have the room too.

Kinda defeats the purpose of a cold air intake though, dont you think?

A "cold air intake" is any thing that pipes cold air from the front of the car to the intake manifold. Dont get too caught up in the hype. What you have with the cone is a low restriction, higher flowing air filter. If you live in the country or overly dusty roads. I wouldn't bother with a cone filter, I'd use the stock paper filter as they filter much more air (although they have some restriction).

[FBD]

On 20/12/2007 at 1:02 PM, Grover said:

One of the few "teething" issues I've not been able to fix since the install of my stroker EFI motor is a whistling sound that comes under acceleration. Depending on the speed I'm traveling, it takes varying amounts of throttle which leads me to believe it's due to "total" air speed traveling into the manifold. While stationary I've removed various bits of the intake system all the way up to removing the TB boot, but still if I blip the throttle I'm hearing a whistle as air is sucked in. I've not heard of this same issue from others who have done similar conversions. I'm using the 318 intake manifold, 325i TB with the adapter plate from 02Again. For a split second it can sound cool (almost like a turbo whine) but the novelty wears off VERY quickly. Any ideas on what could be causing this and what one can do to reduce or eliminate the noise? Thanks folks.

Hi Grover, old post but I was wondering if and how you solved this issue? Reason I ask is I have the exact same set up and the some whistling noice!

 

Cheers

[Simeon]

Vacuum leak?

[FBD]

14 hours ago, Simeon said:

Vacuum leak?

Not a vacuum leak, it's an induction whistling as Grover had.

[TobyB]

These 3 bolts have the ability to make all sorts of noises if they're loose, too short, too long, or not sealing completely.

 

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